5 files changed, 75 insertions, 62 deletions
diff --git a/include/proj/internal/Makefile.am b/include/proj/internal/Makefile.am
index b3fb57eb..59325667 100644
--- a/include/proj/internal/Makefile.am
+++ b/include/proj/internal/Makefile.am
@@ -6,5 +6,6 @@ noinst_HEADERS = \
 	io_internal.hpp \
 	lru_cache.hpp \
 	include_nlohmann_json.hpp \
-	tracing.hpp
+	tracing.hpp \
+	mutex.hpp
 
diff --git a/include/proj/internal/mutex.hpp b/include/proj/internal/mutex.hpp
new file mode 100644
index 00000000..a378be40
--- /dev/null
+++ b/include/proj/internal/mutex.hpp
@@ -0,0 +1,61 @@
+/******************************************************************************
+ *
+ * Project:  PROJ
+ * Purpose:  std::mutex emulation
+ * Author:   Even Rouault <even dot rouault at spatialys dot com>
+ *
+ ******************************************************************************
+ * Copyright (c) 2021, Even Rouault <even dot rouault at spatialys dot com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ ****************************************************************************/
+
+#include "proj/util.hpp"
+#include "proj_internal.h"
+
+#ifndef __MINGW32__
+#include <mutex>
+#endif
+
+NS_PROJ_START
+
+#ifdef __MINGW32__
+// mingw32-win32 doesn't implement std::mutex
+class mutex {
+  public:
+    // cppcheck-suppress functionStatic
+    void lock() { pj_acquire_lock(); }
+    // cppcheck-suppress functionStatic
+    void unlock() { pj_release_lock(); }
+};
+
+template <class Lock> struct lock_guard {
+    Lock &lock_;
+    lock_guard(Lock &lock) : lock_(lock) { lock_.lock(); }
+    ~lock_guard() { lock_.unlock(); }
+};
+
+#else
+
+typedef std::mutex mutex;
+template <class Mutex> using lock_guard = std::lock_guard<Mutex>;
+
+#endif
+
+NS_PROJ_END
diff --git a/src/networkfilemanager.cpp b/src/networkfilemanager.cpp
index fa6375b8..d331f4d6 100644
--- a/src/networkfilemanager.cpp
+++ b/src/networkfilemanager.cpp
@@ -40,25 +40,10 @@
 #include "proj.h"
 #include "proj/internal/internal.hpp"
 #include "proj/internal/lru_cache.hpp"
+#include "proj/internal/mutex.hpp"
 #include "proj_internal.h"
 #include "sqlite3_utils.hpp"
 
-#ifdef __MINGW32__
-// mingw32-win32 doesn't implement std::mutex
-namespace {
-class MyMutex {
-  public:
-    // cppcheck-suppress functionStatic
-    void lock() { pj_acquire_lock(); }
-    // cppcheck-suppress functionStatic
-    void unlock() { pj_release_lock(); }
-};
-} // namespace
-#else
-#include <mutex>
-#define MyMutex std::mutex
-#endif
-
 #ifdef CURL_ENABLED
 #include <curl/curl.h>
 #include <sqlite3.h> // for sqlite3_snprintf
@@ -152,7 +137,7 @@ class NetworkChunkCache {
     };
 
     lru11::Cache<
-        Key, std::shared_ptr<std::vector<unsigned char>>, MyMutex,
+        Key, std::shared_ptr<std::vector<unsigned char>>, NS_PROJ::mutex,
         std::unordered_map<
             Key,
             typename std::list<lru11::KeyValuePair<
@@ -176,7 +161,7 @@ class NetworkFilePropertiesCache {
     void clearMemoryCache();
 
   private:
-    lru11::Cache<std::string, FileProperties, MyMutex> cache_{};
+    lru11::Cache<std::string, FileProperties, NS_PROJ::mutex> cache_{};
 };
 
 // ---------------------------------------------------------------------------
diff --git a/src/transformations/hgridshift.cpp b/src/transformations/hgridshift.cpp
index 326bbb13..96b77c20 100644
--- a/src/transformations/hgridshift.cpp
+++ b/src/transformations/hgridshift.cpp
@@ -6,31 +6,16 @@
 #include <time.h>
 
 #include "proj_internal.h"
+#include "proj/internal/mutex.hpp"
 #include "grids.hpp"
 
 PROJ_HEAD(hgridshift, "Horizontal grid shift");
 
-using namespace NS_PROJ;
-
-#ifdef __MINGW32__
-// mingw32-win32 doesn't implement std::mutex
-namespace {
-class MyMutex {
-  public:
-    // cppcheck-suppress functionStatic
-    void lock() { pj_acquire_lock(); }
-    // cppcheck-suppress functionStatic
-    void unlock() { pj_release_lock(); }
-};
-}
-#else
-#include <mutex>
-#define MyMutex std::mutex
-#endif
-
-static MyMutex gMutex{};
+static NS_PROJ::mutex gMutex{};
 static std::set<std::string> gKnownGrids{};
 
+using namespace NS_PROJ;
+
 namespace { // anonymous namespace
 struct hgridshiftData {
     double t_final = 0;
@@ -208,7 +193,6 @@ PJ *TRANSFORMATION(hgridshift,0) {
 }
 
 void pj_clear_hgridshift_knowngrids_cache() {
-    gMutex.lock();
+    NS_PROJ::lock_guard<NS_PROJ::mutex> lock(gMutex);
     gKnownGrids.clear();
-    gMutex.unlock();
 }
diff --git a/src/transformations/vgridshift.cpp b/src/transformations/vgridshift.cpp
index 7b234517..527fe1e8 100644
--- a/src/transformations/vgridshift.cpp
+++ b/src/transformations/vgridshift.cpp
@@ -6,32 +6,15 @@
 #include <time.h>
 
 #include "proj_internal.h"
+#include "proj/internal/mutex.hpp"
 #include "grids.hpp"
 
 PROJ_HEAD(vgridshift, "Vertical grid shift");
 
-using namespace NS_PROJ;
-
-
-#ifdef __MINGW32__
-// mingw32-win32 doesn't implement std::mutex
-namespace {
-class MyMutex {
-  public:
-    // cppcheck-suppress functionStatic
-    void lock() { pj_acquire_lock(); }
-    // cppcheck-suppress functionStatic
-    void unlock() { pj_release_lock(); }
-};
-}
-#else
-#include <mutex>
-#define MyMutex std::mutex
-#endif
-
-static MyMutex gMutex{};
+static NS_PROJ::mutex gMutex{};
 static std::set<std::string> gKnownGrids{};
 
+using namespace NS_PROJ;
 
 namespace { // anonymous namespace
 struct vgridshiftData {
@@ -251,7 +234,6 @@ PJ *TRANSFORMATION(vgridshift,0) {
 }
 
 void pj_clear_vgridshift_knowngrids_cache() {
-    gMutex.lock();
+    NS_PROJ::lock_guard<NS_PROJ::mutex> lock(gMutex);
     gKnownGrids.clear();
-    gMutex.unlock();
 }